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Momentary switch question

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  • Momentary switch question

    I need to change a push button. The only ones I can find that are less than $30, that light up, and my specific size requirements are momentary instead of on/off switch. Is it possible to make a momentary button function as an on/off switch that activates a relay?

  • #2
    Please explain more details. If I read you right. you need to take a momentary trigger to make relay turn on... what about turning off? same switch? I think this is what you need but you will need to add another relay to have it unlatch/ turn off. This uses 2 pulses to turn on and off Hope this helps SNO

    I actually have a push on/push off switches here depending on size and colour these are what I have in red green or amber
    Last edited by SNOtwistR; 02-06-2014, 04:22 PM.


    • #3
      Yes it will turn things on and off.
      The specs of the switch have to be as follows(what I have in place now). No wiggle room on the cutout:

      The set up is going to be as follows, minus the external light of course:

      The relay I have in place now is:

      The links you sent me to with the multiple relay configuration, isn't there a way to do it with one smaller relay? There's not much room where that's going to have to fit.



      • #4
        I think it's OldSpark time! out of my league. SNO


        • #5
          WOW - finally a question I can answer with qualification! (Hey men, it's been months!)

          A self-latching relay circuit is easy but it requires a power-off else 2nd switch to de-energise.

          For single momentary push button circuits I have two preferences - noting that I prefer NOT to use a heap of relays to do otherwise simple logic etc - hence using a counter else inverter chip.

          The Div-2 aka on-off aka toggle using inverters is as per easiest way to build this circuit?.

          [b]But[/b[ if the switch cannot be dedicated to the circuit - ie, specifically be connected ONLY between the inverter input and RC output above - f.ex the switch if from GND or +12V etc...
          Or if you want a Div-n counter...
          Then I suggest a 4017 type circuit.

          The CD4017 one of ten counter method is probably the simplest and most universal. Tho it's overkill for a Div-2 (on-off), it is easily extended to a Div-n where n is 2 to 10, or 100, 1000, etc (cascade more 4017s for > Div-10).
          And tho overkill for a simple on-off or toggle/flip-flop circuit, it is used f.ex in SAAB headlight relays to toggle between high & low beams.
          Alas I have no circuits tho plenty of descriptions, but the key is to connect the 4017's N output to its reset for a div-n counter where N is 4017 output 0 to 9 (not 1 to 10 as some denote them).

          A basic fig is shown on's 4017 divide by 2 counter, namely:

          But there is a bit more to it - like switch debouncing, output buffering, supply filtering. Maybe my rambles at the12volt's head and park lights on with momentary switch or headlight switch will help.

          Both circuits with appropriate output buffering (transistors etc, or paralleling of spare Open Collector inverter outputs) can drive whatever relay is required.
          Last edited by OldSpark; 02-06-2014, 06:19 PM.


          • #6
            Damn, but the need for a secondary switch does not appeal to me. Thanks anyway. Glad I could finally give you a question to answer lol.

            Snotwistr, which switches do you have? As long as the cutout doesn't exceede 19mm I guess I can modify everything around that.


            • #7
              I have those push on/push off switches from durite when pushed on the light goes on when pushed off the light goes off. I beleive they are 20mm so it will be close to what you have now and will prolly go in to that 19mm hole. Let me know if you want 1 and what colour from red/green/amber and I can send you one. SNO


              • #8
                Originally posted by Champak View Post
                Damn, but the need for a secondary switch does not appeal to me. Thanks anyway.
                No - only a momentary push (button) is required.
                (It was only the self latching SPST relay that needs an NC switch to turn off.)


                • #9
                  I use 3 relays for a add-on to my tracking platform. Taxi driver pushes momentary emergency button. The momentary input goes to relay to turn into constant signal (2 relays) which goes to input on my modem, I have another relay to turn off the first relay via an output signal to ground from an output on my modem. It works well to give a remote switching capabilities. I use only 1 relay for my remote starter disable but that is just connecting/disconnecting a wire. SNO


                  • #10
                    Too late oldspark, but thanks, as soon as I saw your initial response I went hunting again, but this time found a latching switch. My only question is if it says 24v under the specs, does than mean it won't work in the car?
                    Sorry snotwistr, already found a few things that fit my exact specs. Thanks anyway.


                    • #11
                      The switch will work but its LED will be dimmer.